This is the 4222nd most frequent Japanese word.
今夏
"This summer."
In this sentence, '今夏' is used as a time reference to denote the period of 'this summer', making it clear when the activity will take place.
今夏、我々は新しいプロジェクトに取り組みます。
This summer, we will work on a new project.
Here, '今夏' serves to specify the summer being referred to as 'this summer', indicating the time frame of the past summer season.
今夏は非常に暑かったですね。
This summer was extremely hot, wasn't it?
In this context, '今夏' identifies the seasonal context ('this summer') within which the events occurred.